As a scanner, an erasing (a decoloring) apparatus that erases (decolors) an image formed on a sheet, or the like, there is an apparatus that reads both sides of a sheet using two reading sensors. The reading sensors respectively include shading mechanisms for optimizing reading sensitivity and perform shading correction for correcting a read image using correction data obtained by reading white shading plates of the shading mechanisms.
Since the reading sensors respectively include the shading mechanisms, costs increase and a space for the shading mechanisms is necessary. Therefore, it is likely that a reduction in size or a reduction in costs of the scanner, the erasing apparatus, or the like is prevented.